The invention relates to video recording of television signals in which certain detectable segments of the television signal, such as commercial interruptions, are edited from the recording.
A number of systems have been developed from editing commercial messages from the reception and/or recording of television signals. For example, copending U.S. patent application, Ser. No. 77,733 now U.S. Pat. No. 4,390,904 and filed by by Howard R. Johnston and Michael E. R. V. Koombes on Sept. 20, 1979 for AUTOMATIC CIRCUIT AND METHOD FOR EDITING COMMERCIAL MESSAGES FROM TELEVISION SIGNALS, cites early efforts to automatically detect the occurrence of commercial interruptions and then delete them from off-the-air recordings. Also disclosed in application Ser. No. 77,733 is a fully automatic commercial editing system for video tape recorders (VTRs) in which the recorder is placed in a timed pause mode in response to the detection of a fade transition in the television signal that is being recorded. This fade condition is associated with a blank picture, usually a darkened screen, and absence of sound from the television speaker and is detected by monitoring certain characteristics of the video and audio components of the television signal. A timing circuit provides a resettable, timed pause interval, which interval is selected to span the duration of a typical commercial message on the commercial broadcast networks, so that a series of consecutive commercial messages will keep resetting the timing circuit to hold the VTR in the pause mode until after the series of commercials has ended and the program content has resumed.
While the system disclosed in the above-mentioned U.S. application has proved effective, it does have the disadvantage of cutting off an initial portion of the program content when the program resumes after a commercial message. The amount of lost program is a function of the duration of the resettable timing interval, which, for example, may be set at 30-32 seconds. While in many applications, such loss of program content in the completed recording is not objectionable, it would be desirable to provide an editing system that substantially reduces the amount of program content that is deleted when using an editing control system of this type.
Also, the effectiveness of the editing operation achieved by the resettable timing control, depends in part on the uniformity of the durations of the commercial interruptions. If a mixture of relatively short and long commercial interruptions is encountered in a program, the resettable timing circuit is not as effective as when the commercial interruptions are substantially all of a known, fairly uniform length. Thus, it would also be desirable to provide an editing control system of the type characterized, which functions independently of the length of the commercial interruptions and is thus capable of effectively editing from the recording, a mixture of relatively short and long commercial messages.